Good question and one the coaches will have to answer. Last season, at times, I would question if any of the 3 were.
4 were named, not 3, and you question whether they were "legit" while the definition remains a "good question"?
Are we talking about some combination of moves-hands-routes-speed and 1000 yards? Or are we talking about a #4 serviceable as a #3 with maybe solid #3 potential? #2 potential?
I think they all qualify as a #4 or serviceable #3.
In the "what have you done for me lately" world, many fans have thrown in the towel on Adams. That's probably premature. I'd say he's an open book that's needs another year to assess. The rookie year showed promise with some upward trajectory potential.
Montgomery looks like he could be a solid slot receiver, but given Cobb was not moved outside with all of the problems last season one wonders if it will ever happen, thereby relegating Montgomery to utility duty, 4-wide and injury backup.
Abbrederis is very quick out of his breaks, has good hands, and has decent if not outstanding speed. Even if he's close to topped out, #4 or serviceable #3 seems reasonable.
In the last playoff game Janis finally demonstrated he can catch a ball away from his body. I'd been waiting to see that. It shows progess. By all reports, and evidence on the TV screen, he's behind in the mental aspects of the game. If Favre were still around he could play Billy Schroeder-like playground pitch-and-catch. Whether he'll come up to Rodgers exacting standards is anybody's guess. I'm not willing to put him above a #4, but there's a chance he'll rise.